diff --git a/esphome/components/ethernet/ethernet_component.cpp b/esphome/components/ethernet/ethernet_component.cpp
index 90ae342c537..114000401fc 100644
--- a/esphome/components/ethernet/ethernet_component.cpp
+++ b/esphome/components/ethernet/ethernet_component.cpp
@@ -671,12 +671,13 @@ void EthernetComponent::dump_connect_params_() {
   }
 #endif /* USE_NETWORK_IPV6 */
 
+  char mac_buf[MAC_ADDRESS_PRETTY_BUFFER_SIZE];
   ESP_LOGCONFIG(TAG,
                 "  MAC Address: %s\n"
                 "  Is Full Duplex: %s\n"
                 "  Link Speed: %u",
-                this->get_eth_mac_address_pretty().c_str(), YESNO(this->get_duplex_mode() == ETH_DUPLEX_FULL),
-                this->get_link_speed() == ETH_SPEED_100M ? 100 : 10);
+                this->get_eth_mac_address_pretty_into_buffer(mac_buf),
+                YESNO(this->get_duplex_mode() == ETH_DUPLEX_FULL), this->get_link_speed() == ETH_SPEED_100M ? 100 : 10);
 }
 
 #ifdef USE_ETHERNET_SPI
@@ -717,11 +718,16 @@ void EthernetComponent::get_eth_mac_address_raw(uint8_t *mac) {
 }
 
 std::string EthernetComponent::get_eth_mac_address_pretty() {
+  char buf[MAC_ADDRESS_PRETTY_BUFFER_SIZE];
+  return std::string(this->get_eth_mac_address_pretty_into_buffer(buf));
+}
+
+const char *EthernetComponent::get_eth_mac_address_pretty_into_buffer(
+    std::span<char, MAC_ADDRESS_PRETTY_BUFFER_SIZE> buf) {
   uint8_t mac[6];
   get_eth_mac_address_raw(mac);
-  char buf[18];
-  format_mac_addr_upper(mac, buf);
-  return std::string(buf);
+  format_mac_addr_upper(mac, buf.data());
+  return buf.data();
 }
 
 eth_duplex_t EthernetComponent::get_duplex_mode() {
diff --git a/esphome/components/ethernet/ethernet_component.h b/esphome/components/ethernet/ethernet_component.h
index bffed4dc4a3..490a9d026e0 100644
--- a/esphome/components/ethernet/ethernet_component.h
+++ b/esphome/components/ethernet/ethernet_component.h
@@ -3,6 +3,7 @@
 #include "esphome/core/component.h"
 #include "esphome/core/defines.h"
 #include "esphome/core/hal.h"
+#include "esphome/core/helpers.h"
 #include "esphome/components/network/ip_address.h"
 
 #ifdef USE_ESP32
@@ -93,6 +94,7 @@ class EthernetComponent : public Component {
   void set_use_address(const char *use_address);
   void get_eth_mac_address_raw(uint8_t *mac);
   std::string get_eth_mac_address_pretty();
+  const char *get_eth_mac_address_pretty_into_buffer(std::span<char, MAC_ADDRESS_PRETTY_BUFFER_SIZE> buf);
   eth_duplex_t get_duplex_mode();
   eth_speed_t get_link_speed();
   bool powerdown();
diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index 54f864863ce..d849ffd29ab 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -704,7 +704,7 @@ inline char format_hex_pretty_char(uint8_t v) { return v >= 10 ? 'A' + (v - 10)
 /// Write int8 value to buffer without modulo operations.
 /// Buffer must have at least 4 bytes free. Returns pointer past last char written.
 inline char *int8_to_str(char *buf, int8_t val) {
-  int v = val;
+  int32_t v = val;
   if (v < 0) {
     *buf++ = '-';
     v = -v;
@@ -713,11 +713,11 @@ inline char *int8_to_str(char *buf, int8_t val) {
     *buf++ = '1';  // int8 max is 128, so hundreds digit is always 1
     v -= 100;
     // Must write tens digit (even if 0) after hundreds
-    int tens = v / 10;
+    int32_t tens = v / 10;
     *buf++ = '0' + tens;
     v -= tens * 10;
   } else if (v >= 10) {
-    int tens = v / 10;
+    int32_t tens = v / 10;
     *buf++ = '0' + tens;
     v -= tens * 10;
   }